linux-kernel - [PATCH net v3 2/3] sctp: Prevent TOCTOU out-of-bounds write

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Message-ID: <20251028161506.3294376-3-stefan.wiehler@nokia.com>
Date: Tue, 28 Oct 2025 17:12:27 +0100
From: Stefan Wiehler <stefan.wiehler@...ia.com>
To: Xin Long <lucien.xin@...il.com>,
	"David S . Miller " <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: linux-sctp@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Stefan Wiehler <stefan.wiehler@...ia.com>
Subject: [PATCH net v3 2/3] sctp: Prevent TOCTOU out-of-bounds write

For the following path not holding the sock lock,

  sctp_diag_dump() -> sctp_for_each_endpoint() -> sctp_ep_dump()

make sure not to exceed bounds in case the address list has grown
between buffer allocation (time-of-check) and write (time-of-use).

Suggested-by: Kuniyuki Iwashima <kuniyu@...gle.com>
Fixes: 8f840e47f190 ("sctp: add the sctp_diag.c file")
Signed-off-by: Stefan Wiehler <stefan.wiehler@...ia.com>
---
 net/sctp/diag.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/sctp/diag.c b/net/sctp/diag.c
index 1a8761f87bf1..5d64dd99ca9a 100644
--- a/net/sctp/diag.c
+++ b/net/sctp/diag.c
@@ -88,6 +88,9 @@ static int inet_diag_msg_sctpladdrs_fill(struct sk_buff *skb,
 		memcpy(info, &laddr->a, sizeof(laddr->a));
 		memset(info + sizeof(laddr->a), 0, addrlen - sizeof(laddr->a));
 		info += addrlen;
+
+		if (!--addrcnt)
+			break;
 	}
 	rcu_read_unlock();
 
-- 
2.51.0